JP3096331B2 - Diagnostic device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diagnostic apparatus having an oximeter for measuring oxygen in the brain, and more particularly, to a method for detecting a changed blood volume in a brain tissue of a person or the like to be examined.
The present invention relates to a diagnostic device having an oximeter provided with a monitor for measuring and displaying the oxygen saturation.

[0002]

2. Description of the Related Art In general, important parameters to be measured when diagnosing the function of a body organ such as brain tissue include the amount of oxygen in the body organ and the oxygen utilization in the body. Adequate oxygen supply to the body's organs is essential to the growth of the fetus and newborn, and inadequate oxygen supply results in higher fetal mortality and increased neonatal mortality I do. Also, if the supply of oxygen is inadequate, serious sequelae are likely to remain even if the newborn survives. In general, any organ in the body is affected by a lack of oxygen, but the brain tissue is particularly damaged.

[0003] In order to quickly and easily measure the amount of oxygen supply to such internal organs such as brain tissue, US Pat. No. 4,281,645, issued Aug. 4, 1981, discloses a technique disclosed in US Pat. Some diagnostic devices have been developed. In this type of diagnostic device, and hemoglobin oxygen transport medium in the blood, based on the absorption spectrum of near-infrared light by the cytochrome a, a ₃ in cells undergoing redox reaction, internal organs, especially the brain The change in the amount of oxygen is measured.

That is, the wavelength range is 700 to 1300
As shown in FIG. 3 (a), near-infrared light of nm includes oxidized hemoglobin (HbO ₂ ) and deoxygenated hemoglobin (Hb).
And α _HbO2 · α _Hb which are different from each other, and oxidized cytochromes a and a as shown in FIG.
₃ (CyO ₂ ) and reduced cytochrome a, a ₃ (Cy)
And shows different absorption spectra α _cyo2 · α _cy . Utilizing such properties of near-infrared light, four different wavelengths λ1, λ2, λ3, and λ4 (for example, 775 nm, 800 nm, 825 nm, and 850 n) from one side of the patient's head.
m), the near-infrared light is incident in a time-division manner, and the amount of light transmitted through the head is sequentially detected on the other side of the head. By performing predetermined arithmetic processing on these four types of detection results, four unknowns, namely, oxidized hemoglobin (HbO ₂ ), deoxygenated hemoglobin (Hb), oxidized cytochrome a,
a ₃ (CyO ₂ ), reduced cytochrome a, a ₃ (C
y), the amount of change in each concentration is calculated, and based on this, the change in the amount of oxygen in the brain tissue is measured, for example.

FIG. 1 is a schematic configuration diagram of such a diagnostic device 45. In FIG. 1, a conventional diagnostic apparatus includes light sources LD1 to LD such as laser diodes for outputting near-infrared light of four different wavelengths λ1, λ2, λ3, λ4, respectively.
4, a light source controller 55 for controlling the output timing of the light sources LD1 to LD4, and optical fibers 50-1 to 50 to irradiate the near-infrared light output from the light sources LD1 to LD4 to the head 40 of the subject, respectively. 50-4, an irradiation-side fixture 51 for holding the ends of the optical fibers 50-1 to 50-4 in a bundle, and a head of the subject opposite to the side on which the irradiation fixture 51 is attached. 40, an optical fiber 53 that is held by the detection-side fixture 52 and guides near-infrared light transmitted through the head 40 of the subject, and an optical fiber 53 that is guided by the optical fiber 53. The transmitted light detection device 54 that counts the number of photons of infrared light and measures the amount of transmitted near-infrared light, and controls the entire diagnostic device, and furthermore, the amount of change in oxygen in brain tissue based on the amount of transmitted near-infrared light Computer system for measuring It is made up of 56.

The computer system 56 includes a processor 62, a memory 63, an output device 64 such as a display and a printer, and an input device 65 such as a keyboard, which are connected to each other by a system bus 66. The system bus 66 of the computer system 56 has a light source controller 55 as an external I / O.
And the transmitted light detection device 54 are connected.

The light source control device 55 receives a drive signal A as shown in FIG.
The light sources LD1 to LD4 are driven by CT1 to ACT4. In FIG. 2, one measurement period M _k (k = 1, 2,...)
..) is composed of N cycles CY1 to CYN. In the phase φn1 of an arbitrary cycle CYn of the cycles CY1 to CYN, none of the light sources LD1 to LD4 is driven, and the light source LD
Near-infrared light from 1 to LD4 is not irradiated. In the phase φn2, the light source LD1 is driven, and near-infrared light of, for example, 775 nm is output from the light source LD1. Similarly, in the phase φn3, the light source LD2 is driven to output, for example, near-infrared light of 800 nm from the light source LD2,
In n4, the light source LD3 is driven to output near-infrared light of, for example, 825 nm from the light source LD3. In phase φn5, the light source LD4 is driven to output, for example, 850n.
m near infrared light is output. Thus, the light source control device 5
Numeral 5 drives the light sources LD1 to LD4 sequentially in a time-division manner.

The transmitted light detecting device 54 includes an optical fiber 5
3, a filter 57 for adjusting the amount of near-infrared light from the lens 3, lenses 70 and 71, a photomultiplier tube (PMT) 58 for converting light from the filter 57 into a pulse current and outputting the pulse current, and a photomultiplier tube Amplifier (A) that amplifies the pulse current from
MP) 59, and a wave height discriminator 60 for removing a pulse current having a predetermined wave height threshold or less from the current from the amplifier 59.
A multi-channel photon counter 61 for detecting the frequency of photons for each channel; a detection controller 67 for controlling the detection period of the multi-channel photon counter 61; and a cooler 69 containing a photomultiplier tube 58
And a temperature controller 68 that adjusts the temperature of the

In the diagnostic apparatus having such a configuration, when used, the irradiation-side fixture 51 and the detection-side fixture 52 are firmly attached to a predetermined position of the head 40 of the subject by tape or the like. Next, the light source LD is
When each of the light sources LD1 to LD4 is driven as shown in FIG. 2, near-infrared light of four different wavelengths is sequentially output from the light sources LD1 to LD4 in a time division manner, and
The light enters the head 40 of the subject via 0-4. Bone and soft tissue of the head 40 of the subject have a property of transmitting near-infrared light. For this reason, near-infrared light that has entered the subject's head 40 contains hemoglobin in blood within the head 40,
After being partially absorbed by intracellular cytochromes a and a ₃ , it is transmitted to the opposite side of the head 40, guided into the optical fiber 53, and further transmitted from the optical fiber 53 to the transmitted light detection device 54.
Will be introduced. In the phase φn1 in which none of the light sources LD1 to LD4 is driven, the transmitted light detection device 54
The transmitted light from the light sources LD1 to LD4 is not incident on the light source. At this time, the transmitted light detector 54 detects dark light.

The photomultiplier tube 58 of the transmitted light detector 54
Is for photon counting that operates with high sensitivity and high response speed. The output pulse current of the photomultiplier tube 58 is input to the wave height discriminator 60 via the amplifier 59. The wave height discriminator 60 removes noise components below a predetermined wave height threshold, and inputs only signal pulses to the multi-channel photon counter 61. The multi-channel photon counter 61 includes a detection control device 67
2, the number of photons is detected for a period T ₀ synchronized with the drive signals ACT1 to ACT4 of the light sources LD1 to LD4 as shown in FIG. , The number of detected photons for each wavelength is counted. Thus, transmission amount data for each wavelength of near-infrared light is obtained.

That is, as shown in FIG. 2, during one cycle CYn of the light source control device 55, none of the light sources LD1 to LD4 is driven in the phase φn1, so that the transmitted light detection device 54 generates dark light data d. Counted. In the phases φn1 to φn5, the light sources LD1 to LD4 are sequentially driven in a time-division manner, so that the transmitted light detecting device 54 has four different wavelengths λ1, λ2, λ3,
The transmission amount data tλ ₁ , tλ ₂ , tλ ₃ of the near infrared light of λ4,
tλ ₄ is counted sequentially. As described above, the dark light data d and the transmission amount data tλ ₁ , tλ ₂ , tλ ₃ , and tλ _{4 that} are sequentially counted in _one cycle CYn continue to be counted over N cycles CY1 to CYN. That is, with N cycles, one measurement period M _k (k =
1, 2,...). Specifically, for example, if one cycle CYn is 200 μs and N is 10,000, one measurement period _Mk is 2 seconds. At the end of one measurement period _Mk , the counting result of dark light data, Equation 1, the counting result of transmission amount data, and Equation 2 are transferred to the computer system 56 and stored in the memory 63.

[0012]

(Equation 1)

[0013]

(Equation 2)

[0014] processor 62, in one measurement period M stored transmission quantity data in the memory 63 in the _k, the dark light data _{(Tλ 1, Tλ 2, Tλ} 3, Tλ 4, D) Mk and measurement start time M ₀ Transmission data, dark light data (T
λ ₁ , Tλ ₂ , Tλ ₃ , Tλ ₄ , D) Dark subtraction is performed from _M0, and thereafter, the transmission rate of change ΔTλ ₁ , ΔT
λ ₂ , ΔTλ ₃ , and ΔTλ ₄ are calculated. That is, the transmission rate of change ΔTλ ₁ , ΔTλ ₂ , ΔTλ ₃ , ΔTλ ₄ is ΔTλ _j = log [(Tλ _j −D) _Mk / (Tλ _j −D) _M0 ] (j = 1 to 4) Calculated as (1). Note that the logarithm is used in the calculation of ΔTλ _j in order to represent a change in optical density.

From the thus calculated rates of change ΔTλ ₁ , ΔTλ ₂ , ΔTλ ₃ , and ΔTλ _{4 of} the transmission amount, oxidized hemoglobin (HbO ₂ ) and deoxygenated hemoglobin (H
b), concentration changes of oxidized cytochrome a, a ₃ (CyO ₂ ) and reduced cytochrome a, a ₃ (Cy)
_{X HbO2, △ X Hb, △} X cyo2, it is possible to detect each of △ X _cy. That is, the concentration change of each component △ X _HbO2 ,
_{ΔX Hb} , _{ΔX cyo2} , and _{ΔX cy} are detected as Expression 3. Here, α _ij is the wavelength λj (λ1, λ2, λ3, λ
Each component I (HbO ₂ , Hb, CyO ₂ , C) in 4)
y) is the respiration coefficient, which is predetermined from FIGS. 3A and 3B. Ι is the length of the head in the direction in which the near-infrared light travels.

[0016]

(Equation 3)

Thus, the computer system 56
Concentration change of each component detected in _XHbO2 ,
Since X _Hb , △ X _cyo2 , and △ X _cy are, in other words, changes in the amount of oxygen in the brain, by outputting these to the output device 64, it is possible to know and diagnose the change in the amount of oxygen in the brain. it can.

Most of the measured absorption spectra are mainly due to hemoglobin in blood, and very few are due to cytochrome. This is due to the fact that the concentration of hemoglobin in the body is several times higher than that of cytochrome, and the fact that cytochrome has a higher oxygen affinity than hemoglobin. Therefore, the change in the amount of oxygen in the body organ of the measurement target obtained by the measurement is considered to be mainly due to the change in the concentration of hemoglobin in blood.

[0019]

Here, clinically, it has been required to measure the actual oxygen saturation of blood passing through internal organs such as the brain. However, in the conventional diagnostic apparatus as described above, oxidized hemoglobin (HbO ₂ ), deoxygenated hemoglobin (Hb), oxidized cytochrome a, a ₃ (C
Although it is possible to measure and display the change in the concentration of yO ₂ ) and reduced cytochrome a, a ₃ (Cy), it is not possible to measure the oxygen saturation itself in the blood of the subject. there were.

The present invention measures the change in the concentration of oxidized hemoglobin (HbO ₂ ) and the concentration of deoxygenated hemoglobin (Hb) before and after the change in the blood volume of the brain, which is the subject, using the conventional diagnostic apparatus as described above. A diagnostic device capable of calculating the oxygen saturation for the changed blood volume in the brain, which is the subject, based on the measurement result, and displaying the calculation result on an output device of the diagnostic device is provided. The purpose is to do so.

[0021]

In order to achieve the above object, the present invention relates to a diagnostic device for measuring the amount of oxygen in the brain, comprising: a light source for generating light of different wavelengths; Means for injecting the light into a certain brain, extracting the incident light transmitted through the brain, analyzing the extracted light, performing a calculation, and performing a concentration change ΔX ₀₂ of the oxidized medium in the brain and a deoxygenated medium And a means for providing a concentration change ΔX as a calculation result, a means for calculating K × ΔX ₀₂ / ｛ΔX + ΔX ₀₂ ｝ (K is a constant), and a means for displaying the calculation result. Is what you do.

In the diagnostic apparatus, the incident light is near-infrared light, and light of different wavelengths is repeatedly incident on the brain for a predetermined period of time, and the above calculation is performed as | ΔX + ΔX
This is performed when the value of o ₂ | exceeds a predetermined value.

[0023]

According to the present invention having the above structure, the blood volume changes | ΔX + ΔO due to the change in the concentration of the oxidized medium and the deoxygenated medium.
₂ |, calculate the oxygen saturation for the change, and display the calculation result on the display means.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the basic principle of the present invention will be described. As described above, clinically, there has been a request to measure the oxygen saturation of blood in internal organs such as the brain.

However, in the conventional diagnostic apparatus, oxidized hemoglobin (HbO ₂ ) and deoxygenated hemoglobin (Hb)
It is possible to measure and display density changes such as Therefore, the present invention measures the change in the concentration of oxidized hemoglobin (HbO ₂ ) and deoxygenated hemoglobin (HbO) before and after the blood volume in the brain increases or decreases with a conventional diagnostic device,
Based on this measurement result, the increased or decreased oxygen saturation of the blood is calculated and output.

Hereinafter, the present invention will be described in more detail with reference to Examples. The diagnostic device of the present invention has basically the same configuration as the above-described conventional diagnostic device. That is, light sources LD1 to LD4 for generating light of different wavelengths, means for making the light incident on the brain to be diagnosed and extracting transmitted light transmitted through the brain, analyzing the transmitted light, performing calculations, and performing calculations in the brain Means for providing the concentration change ΔX ₀₂ of the oxidized medium and the concentration change ΔX of the deoxygenated medium as calculation results. The difference from the conventional diagnostic device is that the oxygen saturation of the changed blood is calculated based on the detected change in the concentration of the oxidized and deoxygenated hemoglobin.

FIG. 5A shows the change (ratio) of oxidized and deoxygenated hemoglobin due to an increase in cerebral blood volume (CBV) Δ
4 is a graph showing {HbO ₂ } and Δ {Hb}. Increased cerebral blood volume CBV and Δ ｛Hb｝ and Δ ｛HbO ₂ ｝
The increased oxygen saturation in the bloodstream is determined. on the other hand,
FIG. 5B shows changes (proportions) of oxidized and deoxygenated hemoglobins due to a decrease in cerebral blood volume CBV, Δ {HbO ₂ } and Δ.
It is a graph which shows {Hb}. Decreased cerebral blood volume CBV
And Δ {Hb} and Δ {HbO ₂ }, the oxygen saturation in the blood flow reduced is obtained.

That is, when the blood flow increases or decreases, the oxygen saturation ΔSaO in the increased or decreased blood flow
₂ is a change in concentration of each of oxidized hemoglobin (HbO ₂ ) and deoxygenated hemoglobin (Hb) Δ [X _HbO2 ] and Δ
Oxidized hemoglobin (HbO ₂ ) based on the sum of [X _Hb ]
_Is defined as the density change [X _HbO2 ], and is represented by the following equation. ΔSaO ₂ = K × Δ [X _HbO2 ] / {Δ [X _Hb ] + Δ [X _HbO2 ]} (2) Here, K is a constant, and usually K = 100 is applied for percentage display. You.

The calculation for obtaining the oxygen saturation is performed by the CPU 62 according to the flowchart of FIG. The following description, which is measured in the period M _i Δ [X
It is assumed that the values relating to [ _HbO2 ] and Δ [X _Hb ] are stored in the storage area Si of the memory 63 immediately after the measurement is completed.

Hereinafter, the calculation process will be described with reference to FIG. In step S1, Δ [X _HbO ] and Δ [X _HbO2 ]
From the storage area Si of the memory 63 to the CPU 62
Is read out. In step S2, Δ [X _Hb ] + Δ [X
_HbO2 ], which corresponds to the calculation of the denominator in equation (2) above. The calculation result in step S2 indicates a change in the blood volume | ΔCBV | in the brain.

In step S3, the CPU temporarily sets the above |
The value of ΔCBV | is stored in an appropriate location in the memory 63. Next, in step S4, the CPU reads the value,
It is determined whether or not | ΔCBV | is greater than a predetermined threshold Th. Here, | ΔCBV | is a predetermined threshold Th.
If it is not larger, that is, if NO is determined, the process proceeds to step S5.

In step S5, the measurement of Δ [X _HbO2 ] and Δ [X _Hb ] in the next measurement period M _{i + 1} is performed, and these values are stored in the storage area S _{i + 1} of the memory 63. In step S6, i is incremented, and the storage area S _{i + 1} is specified. In step S4, | ΔCBV | is larger than the predetermined threshold value Th, that is, from step S1 to step S4 until the determination of YES is made. The operation is repeated.

When it is determined that | ΔCBV _{i + 1} | is equal to or greater than the predetermined threshold Th, the flow proceeds to step S7. In step S7, the CPU performs a calculation based on the above equation (2) based on the value obtained in step S2. Next, at step S8, the calculation result at step S7 is displayed on the output device 64.

[0034]

According to the present invention, as described above, near-infrared light having different wavelengths is incident on the brain as a subject for a predetermined time. When the value of | Δ [X _HbO2 ] + Δ [X _HbO ] | is equal to or greater than the threshold value, a predetermined calculation is performed, and as a result, highly reliable data with extremely few errors is obtained.

As a result, the change in the concentration of oxidized hemoglobin (HbO ₂ ) and the concentration of deoxygenated hemoglobin (Hb) before and after the change in the blood flow in the brain, which is the subject, are measured. Is calculated for the changed blood of the brain, and the calculation result is displayed by the output device. Therefore, the clinician can know the oxygen saturation immediately after the measurement is completed, which is effective in making a diagnosis.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a diagnostic device of the present invention.

FIG. 2 is a timing chart of a light source drive signal.

FIG. 3A is a graph showing absorption spectra of oxidized hemoglobin and deoxygenated hemoglobin.

FIG. 3B is a graph showing absorption spectra of oxidized cytochrome and deoxygenated cytochrome.

FIG. 4 is a flowchart for calculating oxygen saturation.

FIG. 5A is a graph showing changes in oxidized and deoxygenated hemoglobin when cerebral blood volume CBV increases.

FIG. 5B is a graph showing changes in oxidized and deoxygenated hemoglobin when cerebral blood volume CBV decreases.

[Explanation of symbols]

 45 diagnostic device 54 transmitted light detection device 55 light source control device 56 computer system

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-275324 (JP, A) JP-A-59-141932 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) A61B 5/145

Claims (3)

(57) [Claims] 1. A diagnostic device for measuring the amount of oxygen in the brain, comprising: a light source for generating light of different wavelengths; and a light transmitted through the brain, the light being incident on a brain to be diagnosed. A means for analyzing the transmitted light, performing a calculation, and providing as a calculation result a concentration change ΔX ₀₂ of the oxidized medium and a concentration change ΔX of the deoxygenated medium in the brain, K × ΔXo ₂ / A diagnostic apparatus comprising: means for executing a calculation of {ΔX + ΔXo ₂ } (K is a constant); and means for displaying the calculation result. 2. The diagnostic apparatus according to claim 1, wherein said incident light is near-infrared light. 3. Light of different wavelengths is repeatedly incident on the brain for a predetermined period of time, and the above calculation is performed using | ΔX + ΔXo ₂ |
3. The diagnosis apparatus according to claim 1, wherein the diagnosis is performed when a value of the predetermined value is equal to or more than a predetermined value.